YAML

This module provides utilities for parsing and emitting data in the YAML data serialization format to and from Racket values. See the YAML web site for more information about YAML. The implementation is ported from PyYAML.

See the GitHub repository for more information.

1 Examples

As a quick introduction, this section shows an example of using the module to go from Racket values to YAML and back again.

The write-yaml procedure turns a Racket value into YAML output. Here it displays a sequence of mappings in flow style (by default):

> (write-yaml    '(#hash(("name" . "Mark McGwire")            ("hr" . 65)            ("avg" . 0.278))      #hash(("name" . "Sammy Sosa")            ("hr" . 63)            ("avg" . 0.288))))

make-serializer: broke its own contract;

expected 1 value, returned 3 values

in: the range of

(->*

()

(output-port?

#:allow-unicode

boolean?

#:canonical

boolean?

#:explicit-end

boolean?

#:explicit-start

boolean?

#:indent

(or/c exact-positive-integer? #f)

#:line-break

(or/c "\n" "\r" "\r\n" #f)

#:tags

(or/c (hash/c string? string?) #f)

#:version

(or/c

(cons/c exact-integer? exact-integer?)

#f)

#:width

(or/c exact-positive-integer? #f))

(-> node? void?))

contract from:

<pkgs>/yaml/yaml/serializer.rkt

blaming: <pkgs>/yaml/yaml/serializer.rkt

(assuming the contract is correct)

at: <pkgs>/yaml/yaml/serializer.rkt:15.3

The string->yaml procedure turns YAML text into a Racket value. Here it constructs the same sequence of mappings from above, where this time the YAML is in block style:

> (string->yaml    (string-append     "- name: Mark McGwire\n"     "  hr:   65\n"     "  avg:  0.278\n"     "- name: Sammy Sosa\n"     "  hr:   63\n"     "  avg:  0.288\n"))

'(#hash(("avg" . 0.278) ("hr" . 65) ("name" . "Mark McGwire"))   #hash(("avg" . 0.288) ("hr" . 63) ("name" . "Sammy Sosa")))

The yaml-struct macro defines a struct that can be written to and read from YAML:

> (yaml-struct player (name hr avg) #:transparent)

> (write-yaml (player "Mark McGwire" 65 0.278))

make-serializer: broke its own contract;

expected 1 value, returned 3 values

in: the range of

(->*

()

(output-port?

#:allow-unicode

boolean?

#:canonical

boolean?

#:explicit-end

boolean?

#:explicit-start

boolean?

#:indent

(or/c exact-positive-integer? #f)

#:line-break

(or/c "\n" "\r" "\r\n" #f)

#:tags

(or/c (hash/c string? string?) #f)

#:version

(or/c

(cons/c exact-integer? exact-integer?)

#f)

#:width

(or/c exact-positive-integer? #f))

(-> node? void?))

contract from:

<pkgs>/yaml/yaml/serializer.rkt

blaming: <pkgs>/yaml/yaml/serializer.rkt

(assuming the contract is correct)

at: <pkgs>/yaml/yaml/serializer.rkt:15.3

> (string->yaml    "!!struct:player {hr: 65, avg: 0.278, name: Mark McGwire}")

(player "Mark McGwire" 65 0.278)

2 YAML Expressions

3 Reading YAML

4 Writing YAML